The present invention is directed to a video image generator for use in producing a realistic background video image on a raster type video screen.
Image circuitry for producing pictures of objects or scenery generally includes addressable memories containing picture data. The larger and more complex the object or scene is, the greater the memory space required. Images which depict scenery and which fill a substantial portion of the screen, for example, require considerable memory space if the full image is stored. Such an image is desirable in video games or the like as a background against which other objects can be displayed. It is especially desirable in games to have the background image movable in response to controls operated by the game player, so as to give an illusion of motion. In view of the cost, it is undesirable to provide a large movable background image in video game circuits through direct storage of the full image in memory.
It significantly reduces memory requirements to provide a background image having relatively simple elements which are repeated numerous times to fill the screen. Nevertheless, such images are generally unsatisfactory for providing a realistic background picture. This is particularly true when, in video games, it is desired to depict a continuous and unbroken background image containing the illusion of perspective.